1. Field of the Invention
The present invention generally relates to a thermostat device for cooling internal combustion engines, and particularly to a thermostat device having a small hydraulic resistance in comparison to conventional thermostats, and capable of immediately warming the cooling water for controlling the activation of the valve element regardless of the cooling water temperature at the time of starting the engine and seeking improved fuel consumption of the engine thereby.
2. Description of the Related Art
A thermostat device disposed in the cooling system of an internal combustion engine and the like comprises a sensor case having a thermally expanding body built therein which expands/contracts by sensing the temperature change in the cooling water filled in the circulation flow channel of the cooling system, conducts the opening/closing of the valve element pursuant to the volume change concurrent with the expansion/contraction of such thermally expanding body, and functions to retain the cooling water at a prescribed temperature.
FIG. 7 shows an example of a conventional thermostat device, and this thermostat device 1A comprises a thermostat activation unit 30, which is the actuator of the valve element, inside the valve housings 31, 32 structured of two members. This thermostat activation unit 30 is fixed to the valve housing 32, activates the first valve element 33 and the second valve element 35 (bypass valve) with an activation piston 9 built in the thermostat activation unit 30, and controls the main flow channel 34 and the bypass flow channel 36.
The housing 37 of the thermostat activation unit 30 is retained with a holder 39, and this holder 39 encircles, in a cap shape, the end opposite to the side in which the aforementioned activation piston is protruding in the housing 37. The cap-shaped holder 39 is supported with the valve housing 32.
A pot-shaped center area is provided at the cross section of the first valve 33, and the thermostat activation unit 30 is disposed at the center thereof. This center area blocks the main flow channel 34 together with the holder 39 with the first valve element 33 being in a closed position.
A bolt 38 is provided on the axial extension of the activation piston (not shown) of the thermostat activation unit 30, and the second valve element 35 (bypass valve) is mounted on this bolt 38 with a slide guide, thereby enabling the opening/closing of the bypass flow channel 36. The second valve element 35 (bypass valve) is energized with a spring member 41. The first valve element 33 is energized with a spring member 40, and this spring member is supported with the valve housing 31.
The thermostat device 1A structured as described above is disposed so as to allow the cooling water from the engine to circulate from the bypass flow channel 36 to the engine upon inflowing from a sleeve 42, or to circulate to the radiator via a sleeve 43.
The cooling water inflowing from the bypass 36 is returned directly to the engine since the cooling water is of a low temperature prior to the air becoming warm at the time of starting the engine.
When the cooling water reaches a prescribed temperature after the warm air operation, the wax inside the housing 37 expands pursuant to this temperature and extends the activation piston (not shown) of the thermostat activation unit 30. Pursuant to this extension of the activation piston, the first valve element 33 resists the energization of the spring member 40, comes down, and releases the main flow channel from the blocked state into an open state, and the second valve element 35 (bypass valve) blocks the bypass flow channel 36. Thus, the cooling water inflowing from the sleeve 42 flows into the radiator via the sleeve 43.
Furthermore, in order to forcibly expand the wax inside the housing 37, this structure provides a heating unit 44 to the housing 37, and protrudes this heating unit 44 from the valve housing 32 for connection with a superheating element 45.
Incidentally, with this type of conventional thermostat device 1A, since the housing 37, which is the temperature sensor of the cooling water, is disposed inside the cooling water flow channel, the hydraulic resistance of the cooling water inflowing from the sleeve 42 becomes large, and it is thereby difficult to miniaturize the water pump for forcibly circulating the cooling water.
Moreover, there are cases where a hunting phenomenon would arise when the cooling water from the engine and the cooling water from the radiator are mixed in the vicinity of the housing 37 during the warm air operation at the time of starting the engine. When this type of phenomenon arises, the cooling water temperature inflowing to the engine becomes unstable, and it is difficult to improve the fuel consumption and to seek the immediate warming of the cooling water. As a preventive measure, it is necessary to add a twist to the structure of the valve housing 32 in order to mix the cooling water immediately before the housing 37, which is the temperature sensor, or to mount a current plate such as a so-called interruption plate.
In addition, when this thermostat device 1A is disposed as an entrance control unit, it may sense the cooling water inflowing from the engine, and there were cases of malfunctions such as overshoots and so forth.
Thus, the thermostat device according to the present invention was devised in view of the foregoing problems, and an object thereof is to provide a thermostat device capable of immediately warming the cooling water even at the time of starting the engine and improving the fuel consumption, and wherein the cooling water has a small hydraulic resistance.
The thermostat device of the present invention has a structure wherein, inside the housing of a bottom bypass-type thermostat device comprising a main valve element on the main body and a bypass valve element on the bottom side, the main valve element and bypass valve element are supported by a main shaft supported at the piston tip of a thermoelement, the temperature sensor of the thermoelement is disposed such that it does not directly contact the cooling water from the radiator outlet and senses the temperature by contacting a portion of the cooling water from the engine outlet, the temperature sensor is equipped with a heating element, and the opening/closing of the main valve element and bypass element pursuant to the cooling water temperature as well as the control of the opening/closing of the valve element pursuant to the application of said heating element are freely conducted thereby.
According to this type of structure, it is possible to prevent the hunting phenomenon caused by the cooling water from the engine during the warm air operation at the time of starting the engine, and to improve the fuel consumption as well as to seek the immediate warming of the cooling water. Thus, it is not necessary to improve the structure of the valve housing or to mount a current plate in order to mix the cooling water immediately before the housing, which is the temperature sensor.
Furthermore, formed on the housing are a first inflow sleeve to which a part of the cooling water from the engine outlet inflows, a second inflow sleeve to which the cooling water from the radiator inflows, a sub flow channel for outflowing a part of the cooling water from the first inflow sleeve to the cooling water main flow channel or bypass flow channel inside the engine, and a main flow channel for outflowing the cooling water from the radiator to the cooling water main flow channel inside the engine.
By forming the respective flow channels inside the housing as above, the internal structure of the thermostat may be simplified, and resin materials such as heat-resistant plastic may be manufactured integrally with the housing itself. This will allow the thermostat device to be compatible with units.
Moreover, the main valve is disposed above the bypass valve, the thermoelement is disposed thereabove, and the first inflow sleeve is provided in between the thermoelement and the main valve.
According to the aforementioned structure, it is no longer necessary to dispose the thermoelement in the cooling water flow channel inside the housing, the hydraulic resistance of the cooling water can be decreased, and the structure of the thermostat device can be simplified. Further, by changing the flow volume of the sleeve 1; that is, the diameter of the sleeve, and changing the flow volume rate with the other flow channels, the response of the thermoelement can be easily changed. The balance with the heat value of the heating element can also be easily adjusted.
In addition, the thermoelement is disposed such that the cooling water from the first sleeve only contacts a part of the thermoelement temperature sensor, and the heating element is provided on the outside of the cooling water channel via a seal member.
With this type of structure, the amount of cooling water in which the thermoelement is to sense the temperature thereof may be easily changed by merely changing the internal structure of the housing, and response of the thermoelement can also be easily changed thereby. Moreover, the balance with the heat value of the heating element can also be easily adjusted.
Further, by disposing the heating element outside the cooling water flow channel, electrical reliability and maintenance can be improved.